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--- en:this_little_thing_called_qubit [2021/01/09 19:12]
jaddawyn
+++ en:this_little_thing_called_qubit [2021/01/16 10:29] (current)
@@ Line 1: / Line 1: @@
-====== This little thing called qbit ======
+====== This little thing called qubit ======
-qbit stands for "quantum bit". In classical computation one uses **bits** for computation whereas **qbits** are used in quantum computation.\\
+qubit (or qubit) stands for "quantum bit". In classical computation one uses **bits** for computation whereas **qubits** are used in quantum computation.\\
 \\
 ===== What is a bit ? =====
-A bit is used in classical computation to carry information. A bit is an electrical state with two levels, for instance 1 Volt and 4 Volts. At each state is associated a numeric value: 0 or 1. This is the basic of numeric system.\\
+A bit is used in classical computation to carry information. It is an electrical state with two levels, for instance 1 Volt and 4 Volts. At each state is associated a numeric value: 0 or 1. This is the basic of binary numeric system.\\
 \\
-In computers, classical microprocessors are running billions of calculus using bits every second. \\
+In computers, classical microprocessors are running billions of operations using bits every second. \\
 Therefore your computer encode all values into a series of bits. For instance the value 7 is encoded as follow in a byte (a byte is a set of 8 bits):
 ;#;
 **0 0 0 0 0 1 1 1**
 ;#;
-I won't explain how to encode and decode values from mathematical value to binary value, someone else already did that better:\\
+I won't explain how to encode and decode values from mathematical value to binary value, someone else already did that right:\\
-XXX\\
+;#;
+[[https://ccm.net/contents/57-binary-encoding]]
+;#;
+\\
 You'll need to be ease with this to understand what follows.
+==== What is a qubit ? ====
+Classic bits are based on voltage associated to binary level 0 or 1, while qubits are based on quantum states.\\
+\\
+A qubit is a particle and has 2 base states noted |0> and |1> (called Dirac notation, we'll see that in detail later). As a quantum particle, it is in superposed state before being read. Like the cat that is both dead and alive before you open the box.\\
+\\
+Let's come back to the previous experiment:\\
+{{ :en:1_particle.png?400 |}}
+\\
+When the particle leaves the source it is in superposed state: i.e. a probability combination of |0> and |1>. When it comes to the detector, decoherence happens and the particle collapses to a fixed state |0> or |1>.
+\\
+\\
+But manipulating qubits alone is quite useless. But the same way we can group bits into sets, qubits can be grouped into **registers**.\\
+A quantum register is a set of several qubits we will use for computing.
+\\
+\\
+You must wonder what is the point of qubits since we get 0 or 1 in the end like bits... all is about probabilities in the middle. Be patient we'll see that later.
+\\
+\\
+<columns 100% 50% ->
+Previous: [[en:schrodingers_cat|Schrödinger's cat]]
+<newcolumn>
+;;#
+Next: [[en:mathematics_at_the_rescue|Mathematics at the rescue]]
+;;#
+</columns>

Quantum leap

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